Stress-Strain Curves for Modeling Prestressing Wires

The development of stress-strain models for prestressing wires has not been performed in earlier studies. The existing modeling approaches (the PCI strand equation and the ACI equation) lack sufficient accuracy when compared to the actual response of prestressing wires. This paper improves the accuracy in predicting fps by modifying the existing "Power Formula" to suit the response of these wires. The newly developed "Wire Specific Formula" was based on using the actual stress-strain curves collected from experimental testing in an analytical modeling process. A total of 13 types of prestressing wires with 5.32 mm (0.2094 in.) diameter were tested and the wires 'geometric properties were measured. The adapted Power Formula captured the accuracy of the actual experimental or design-oriented stress-strain response very well through linear regression of key parameters, showing strong correlation. Then, the same Power equation is redeveloped for design-oriented purposes when the level of ultimate prestressing strength is specified or assumed. The present version of the Power Formula can, accordingly, be used either for specific wire type (Wire Specific Formula) or certain strength grade (Wire Strength Formula).